Catalytic Reduction of Oxygen by Metalloporphyrins in Fuel Cell Electrodes

L. Elbaz, Armand Bettelheim, Eli Korin

Research output: Book/ReportBookpeer-review


One of the main problems in today's fuel cells is that the electrodes contain noble metal catalysts, such as platinum. This raises the price of the fuel cell, thus making it harder to introduce into the market. Another major drawback is that the electrodes substrate material consists of compressed carbon black particles. These highly condensed particles impede the mass transport of fuel or oxygen in the pores. Aerogel carbon (AEC) is a porous conductive material with relatively large surface area (approx. 600m2 /g). In this work, we describe a new concept based on non-noble macrocyclic catalysts for O2 reduction and their incorporation in AEC electrodes. Cobalt(III)-tetra(4- sulfonatophenyl)porphyrin(CoTPPS), and cobalt(III)- tetra(2-aminophenyl)porphyrin (CoToAPP) were incorporated in AEC via adsorption (CoTPPS and CoToAPP) or electropolymerization (CoToAPP). From results obtained with SEM-EDS, the dispersion of the cobalt porphyrins throughout the AEC cross section was found to be uniform. Adsorption of the metalloporphyrins was found to follow first order kinetics: kads = 2.8*10-5 sec-1 for both metalloporphyrins. The electrocatalytic activity of these electrodes towards the oxygen reduction reaction was investigated as well. The half wave potentials obtained in air saturated 1 M H2SO4 solution for AEC, AEC/CoTPPS, and AEC/CoToAPP electrodes were 75, 150, and 200mV vs. Ag|AgCl, respectively. The current densities obtained for these electrodes at 0V were 0.31, 0.82, and 1.32mA/cm2 , respectively. Nafion was also incorporated in the AEC pores and was found to be uniformly dispersed throughout the electrode cross- section. This polymer blocked 30% of the AEC micropores, but did not have any significant effect on the surface area of the meso- and macro- pores. The addition of Nafion enhanced proton migration in the pores and consequently increased oxygen reduction currents at 0 V in air saturated 1 M H2SO4: 0.5, 2.89, and 9.5mA/cm2 for AEC/Nafion, AEC/Nafion/CoTPPS, and AEC/Nafion/CoToAPP electrodes, respectively
Original languageAmerican English
PublisherMeeting Abstracts. No. 1. The Electrochemical Society
StatePublished - 2006


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